Low-pressure pilot valve

Abstract

An improved pilot valve is disclosed having a flow path from the inlet to the sense cavity via the valve spindle. An articulated disk is provided at the bottom of the valve spindle and is secured thereto by a hollow screw. Such articulated disk can adjust itself to the valve seat below to provide sealing of the valve to the seat in cases where the valve spindle is not perfectly axially aligned with the seat. A spacer between the upper and lower diaphragms is provided for maintenance of proper effective areas of such diaphragms and for prevention of resistance to valve stem motion.

What is claimed is: 
     
       1. An improved pilot valve including a valve body (41),   said valve body (41) including a port (66), an exhaust outlet (7), and a valve seat (27) surrounding a fluid flow path between said port (66) and said exhaust outlet (7), said valve seat (27) having a valve seat passage (75) extending between its top surface and said port (66),   a valve (28) supported with respect to said body (41) and adapted to be seated on and unseated from said valve seat (27) to control flow therethrough,   pressure responsive means (32, 34, 37, 36) connected to said valve (28) and adapted to move said valve (28),   spring means (6) for urging said pressure responsive means in a direction to close said valve,   an inlet (73) in said valve body adapted for connection to a source of said pressure fluid, the pressure of which is to be controlled,   a passage disposed between said inlet (73) and said port (66), said passage having a restriction disposed therein,   first path means (83, 84) for establishing communication between said inlet (73) and said pressure responsive means (32, 37), whereby the pressure of fluid conducted to said pressure responsive means through said first path means urges said pressure responsive means in a direction to unseat said valve (28) from said valve seat (27),   second path means for establishing communication between said pressure responsive means (37, 36) and said inlet (73), whereby the pressure of said pressure fluid via said second means urges said pressure responsive means in a direction to seat said valve (28) on said valve seat (27), and to unseat said valve (28) on said valve seat (27), and   means for controlling the pressure in said second path means whereby flow occurs through said second path means on the opening of said valve (28) thereby reducing the pressure urging said pressure sensitive means in a direction to seat said valve 28 on said valve seat (27) and to reduce the pressure in said port (66),   said pressure responsive means having   a diaphragm case (32, 34) supported with respect to said body and having a first diaphragm (37) and a second diaphragm (36) operably mounted therein,   said first diaphragm (37) and said case (32) defining a first chamber into which said first means connects,   said first (37) and said second (36) diaphragms and said case (32, 34) defining a second chamber into which said second means connects, the effective pressure area of said first diaphragm (37) being greater than the effective pressure area of said second diaphragm (37),   wherein the improvement comprises said valve (28) having a stem (22) connected to said first (37) and second (36) diaphragms, and having internal passages (80) for communicating pressure fluid to said second chamber, and a downwardly facing first curved surface (105) on its lower end (22'),   a disk (33) having an upwardly facing second curved surface (106) adapted to mate with said first curved surface of said stem and providing articulation of said disk with respect to said stem, said disk having a downwardly facing surface adapted to cooperate with said valve seat (27) to open or close said fluid flow path between said port (66) and said exhaust outlet (7), and   a fastener (26) securing said disk (33) to said lower end of said stem, said fastener having an axial passage (77) through it, wherein   said second path means is defined by said internal passage (80) of said stem (22), said axial passage (77) through said fastener, said valve seat passage (75), said port (66), said inlet (73) and said passage (79) between said inlet (73) and port (66), and whereby said disk (33) may move with respect to said stem (22) so that said disk can seal against said seat (27) yet maintain said second path means.   
     
     
       2. The improved pilot valve of claim 1 wherein the improvement further comprises a seal (32) placed between said stem (22) and said disk (33).   
     
     
       3. The improved pilot valve of claim 2 wherein said seal (32) is an "O"-ring placed radially outwardly of said fastener (26). 
     
     
       4. The improved pilot valve of claim 1 wherein said fastener (26) is a threaded screw having an axial passage (77) provided therein.   
     
     
       5. The improved pilot valve of claim 1 wherein said valve seat (27) includes an "O" ring (67) in a groove at its top end for contacting said valve (28) and the improvement further comprises said downwardly facing surface of said disk (33) including coating means for prevention of sticking of said surface to said "O" ring 67 of valve seat 27.   
     
     
       6. The improved pilot valve of claim 1 wherein said first diaphragm (37) and said second diaphragm (36) are secured to said case at their outer periphery and wherein said improvement further comprises a spacer (11) disposed between said first and second diaphragms.